In this paper an analytical method is used meant for the vibration study of a cracked and misaligned rotor which is given by Chondros theoretically. By considering a simply supported beam which acts like a turbine shaft with crack and without crack a comparison is made between their natural frequencies which varies along with the crack ratio and position of the crack. The existence of cracks causes changes in the mechanical properties, physical properties and stiffness of the structure. Furthermore, it leads to the alteration in energetic retort of the whole beam. The results obtained from finite element analysis can be compared theoretically by the governing equation given by Chondros. The analysis was performed using ANSYS 18.1 software. Here the shaft crack is considered in the form of spring.

Keywords : Natural frequencies, crack formation, simply supported beam, ANSYS.